Optical waveguide module

ABSTRACT

An optical waveguide module includes an optical waveguide sheet including multiple optical waveguides, and a light-emitting device and a light-receiving device each positioned over a surface of the optical waveguide sheet. At least one of the optical waveguides includes a first mirror, a second mirror, and a slit. The first mirror is configured to reflect light entering the corresponding optical waveguide from its first end to the light-receiving device or to reflect light emitted from the light-emitting device toward the first end of the corresponding optical waveguide. The second mirror is configured to reflect light entering the corresponding optical waveguide from its second end toward the surface of the optical waveguide sheet. The slit is provided between the second mirror and the second end of the corresponding optical waveguide. The corresponding optical waveguide is discontinuous across the slit.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based upon and claims the benefit of priorityof Japanese Patent Application No. 2015-022621, filed on Feb. 6, 2015,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to optical waveguides.

2. Description of the Related Art

Optical waveguide modules for optical communications, in which alight-emitting device and a light-receiving device are provided on anoptical waveguide, are known. Such optical waveguide modules aremanufactured by joining a light-emitting device and a light-receivingdevice to optical waveguides after aligning the light-emitting deviceand the light-receiving device relative to the optical waveguides sothat light from the light-emitting device enters the optical waveguideand light from the optical waveguide enters the light-receiving device.Reference may be made to Japanese Laid-Open Patent Application No.2009-69360 for related art.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, an optical waveguidemodule includes an optical waveguide sheet including a plurality ofoptical waveguides, a light-emitting device positioned over a surface ofthe optical waveguide sheet, and a light-receiving device positionedover the surface of the optical waveguide sheet. At least one of theplurality of optical waveguides includes a first mirror configured toreflect light entering the corresponding optical waveguide from a firstend thereof to the light-receiving device or to reflect light emittedfrom the light-emitting device toward the first end of the correspondingoptical waveguide, a second mirror configured to reflect light enteringthe corresponding optical waveguide from a second end thereof oppositeto the first end toward the surface of the optical waveguide sheet, anda slit provided between the second mirror and the second end of thecorresponding optical waveguide. The corresponding optical waveguide isdiscontinuous across the slit.

According to an aspect of the present invention, an optical waveguidemodule includes an optical waveguide sheet including a plurality ofoptical waveguides, a light-emitting device positioned over a firstsurface of the optical waveguide sheet, a light-receiving devicepositioned over the first surface of the optical waveguide sheet, afirst mirror formed in at least one of the plurality of opticalwaveguides and configured to reflect light entering from a secondsurface of the optical waveguide sheet opposite to the first surfacetoward the optical waveguide, and a second mirror formed in the opticalwaveguide and configured to reflect the light reflected from the firstmirror and propagating through the optical waveguide toward the firstsurface of the optical waveguide sheet.

According to an aspect of the present invention, an optical waveguidemodule includes an optical waveguide sheet including a plurality ofoptical waveguides, a light-emitting device positioned over a surface ofthe optical waveguide sheet, a light-receiving device positioned overthe surface of the optical waveguide sheet, a mirror formed in at leastone of the plurality of optical waveguides, the mirror being configuredto reflect light propagating through the optical waveguide toward thesurface of the optical waveguide sheet, and a recognition mark providedon the mirror.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a structure of an optical waveguidemodule;

FIG. 2 is an exploded perspective view of the optical waveguide module;

FIG. 3 is a perspective view of the optical waveguide module;

FIG. 4 is a diagram illustrating an optical waveguide sheet and a lenssheet that are out of alignment when being mounted;

FIG. 5 is a diagram illustrating a structure of an optical waveguidemodule according to a first embodiment;

FIG. 6 is an exploded perspective view of the optical waveguide moduleaccording to the first embodiment;

FIG. 7 is a perspective view of the optical waveguide module accordingto the first embodiment;

FIG. 8 is a diagram illustrating an optical waveguide in an opticalwaveguide sheet;

FIG. 9 is a diagram illustrating a structure of the optical waveguidesheet according to the first embodiment;

FIG. 10 is an enlarged view of part of the optical waveguide sheetaccording to the first embodiment;

FIGS. 11A and 11B are diagrams illustrating the optical waveguide sheetaccording to the first embodiment;

FIG. 12 is a diagram illustrating the optical waveguide sheet accordingto the first embodiment;

FIG. 13 is an enlarged view of part of the optical waveguide sheetaccording to a second embodiment;

FIGS. 14A and 14B are diagrams illustrating the optical waveguide sheetaccording to the second embodiment;

FIG. 15 is a diagram illustrating the optical waveguide sheet accordingto the second embodiment;

FIG. 16 is an enlarged view of part of the optical waveguide sheetaccording to the second embodiment;

FIGS. 17A and 17B are diagrams illustrating the optical waveguide sheetaccording to the second embodiment;

FIG. 18 is an enlarged view of part of the optical waveguide sheetaccording to a third embodiment;

FIGS. 19A and 19B are diagrams illustrating the optical waveguide sheetaccording to the third embodiment;

FIG. 20 is an enlarged view of part of the optical waveguide sheetaccording to a fourth embodiment;

FIGS. 21A and 21B are diagrams illustrating the optical waveguide sheetaccording to the fourth embodiment;

FIG. 22 is an enlarged view of part of the optical waveguide sheetaccording to a fifth embodiment; and

FIG. 23 is a diagram illustrating the optical waveguide sheet accordingto the fifth embodiment.

DESCRIPTION OF THE EMBODIMENTS

According to an aspect of the present invention, it is possible toprovide an optical waveguide module including optical waveguidesprovided with a light-emitting device and a light-receiving device thatcan be manufactured at low cost and obtain desired characteristics.Embodiments of the present invention are described below. The sameelements are referred to by the same reference numeral, and are notrepeatedly described.

First, the mounting of a light-emitting device and a light-receivingdevice on optical waveguides in manufacturing an optical waveguidemodule is described with reference to FIGS. 1 through 3. Referring toFIGS. 1 through 3, an optical waveguide module is manufactured bystacking a lens sheet 920 and a flexible substrate 930 on an opticalwaveguide sheet 910 and joining the lens sheet 920, the flexiblesubstrate 930, and the optical waveguide sheet 910 together. Alight-emitting device 941 such as a vertical cavity surface emittinglaser (VCSEL), a light-receiving device 942 such as a photodiode (PD), adriver 943 that drives the light-emitting device 941, and atransimpedance amplifier (TIA) 943 that amplifies a signal from thelight-receiving device 942 are mounted on the flexible substrate 930 byflip-chip bonding.

Optical waveguides 911 are arranged in a width direction of the opticalwaveguide sheet 910. A mirror 912 is formed in each optical waveguide911 so as to cause light emitted from the light-emitting device 941 toenter the optical waveguide 911 or cause light in the optical waveguide911 to enter the light-receiving device 942. Lenses 921 are provided inthe lens sheet 920 so as to be positioned between the optical waveguidesheet 910 and the flexible substrate 930. A ferrule 950 with lenses forinputting light to optical waveguides 911 and outputting light fromoptical waveguides 911 is connected to an end 910 a of the opticalwaveguide sheet 910.

The optical waveguide sheet 910, the lens sheet 920, the light-emittingdevice 941, and the light-receiving device 942 are desired to be alignedand joined, so that light entering optical waveguides 911 is verticallyreflected relative to the surface of the optical waveguide sheet 910 bythe mirrors 912 so as to enter the light-receiving device 942 via thecorresponding lenses 921 and that light emitted from the light-emittingdevice 941 is incident on the mirrors 912 via the corresponding lenses921 so as to be reflected by the mirrors 912 to enter the opticalwaveguides 911.

Methods of manufacturing an optical waveguide module include passivemounting and active mounting. According to passive mounting, alignmentmarks are formed on optical waveguides, a light-emitting device, and alight-receiving device in advance, and the light-emitting device and thelight-receiving device are aligned with and mounted on the opticalwaveguides using the alignment marks. On the other hand, according toactive mounting, a light-emitting device and a light-receiving deviceare mounted on optical waveguides by causing light from a light sourceto enter optical waveguides and aligning the light-emitting device andthe light-receiving device so that the light-emitting device and thelight-receiving are positioned so as to minimize a loss of the amount oflight while measuring the amount of light.

According to active mounting, because alignment is performed whilemeasuring the amount of light, it takes time to perform alignment, thusresulting in low productivity and higher manufacturing cost of theoptical waveguide module.

Accordingly, passive mounting is preferable to manufacture an opticalwaveguide module at low cost.

In the case of aligning components with reference to the positions ofthe mirrors 912 without causing light to enter the optical waveguides911, the part of the mirrors 912 becomes dark, so that the positions ofthe mirrors 912 are difficult to visually clearly recognize, thuspreventing accurate alignment of components. Therefore, there is amethod according to which the positions of the mirrors 912 are detectedusing light reflected from the mirrors 912 while keeping light enteringthe optical waveguides 911 through the ferrule 950. According to thismethod, however, the boundaries of the mirrors 912 become unclear, sothat the positions of the mirrors 912 may not be properly recognized,thus making it difficult to accurately align the lens sheet 920 with theoptical waveguide sheet 910. The boundaries of the mirrors 912 becomeunclear because each mirror 912 has a certain size of area so that lightis out of focus in some part of the boundary of the mirror 912 althoughthe light is in focus in some part of the mirror 912. Furthermore, thelight source of the light entering the optical waveguides 911 is adedicated light source whose amount of light is not adjustable.Therefore, if light reflected from the mirrors 912 is too strong, strongcontrast results to cause scattering light to leak around the boundariesof the mirrors 912, so that strong scattering light makes the boundariesof the mirrors 912 unclear.

Accordingly, when alignment is performed by the above-described method,the positions of the mirrors 912 of the optical waveguides 911 may bemisaligned with the positions of the lenses 921 of the lens sheet 920 asillustrated in FIG. 4. When the optical waveguide sheet 910 and the lenssheet 920 as positioned as illustrated in FIG. 4 are joined, lightreflected from the mirrors 912 does not enter the lenses 921, and lightemitted from the light-emitting device 941 does not enter the mirrors912. Therefore, the manufactured optical waveguide module is preventedfrom having desired characteristics.

Accordingly, there is a demand for an optical waveguide module in whichthe optical waveguide sheet 910, the lens sheet 920, the light-emittingdevice 941, and the light-receiving device 942 are aligned so that lightentering the optical waveguides 911 of the optical waveguide sheet 910from the ferrule 950 is reflected from the mirrors 912 provided in theoptical waveguides 911 so as to enter the light-receiving device 942through the lenses 921 of the lens sheet 920 and that light emitted fromthe light-emitting device 941 is made incident on the mirrors 912through the lenses 921 so as to be reflected from the mirrors 912 toenter the optical waveguides 911.

First Embodiment

Next, a first embodiment is described. Referring to FIGS. 5 through 7,an optical waveguide module according to this embodiment is manufacturedby stacking a lens sheet 20 and a flexible substrate 30 in layers on afirst surface 10 c of an optical waveguide sheet 10. A light-emittingdevice 41 such as a VCSEL, a light-receiving device 42 such as a PD, adriver 43 that drives the light-emitting device 41, and a TIA 44 thatamplifies a signal from the light-receiving device 42 are mounted on theflexible substrate 30 by flip-chip bonding. A ferrule 50 with lenses forinputting light from the outside to optical waveguides 11 and outputtinglight from optical waveguides 11 to the outside is connected to a firstend 10 a of the optical waveguide sheet 10.

FIG. 8 is a perspective view of the optical waveguide sheet 10.Referring to FIG. 8, cores to serve as the optical waveguides 11 areprovided in the optical waveguide sheet 10. The cores are surrounded bycladding 12. A polyimide layer 13 is formed on each of an upper surfaceand a lower surface of the cladding 12. According to this embodiment,the cores have a refractive index of approximately 1.6, and the cladding12 has a refractive index of approximately 1.5.

Next, the optical waveguide sheet 10 of the optical waveguide moduleaccording to this embodiment is described with reference to FIGS. 5, 9,10, 11A and 11B. FIG. 9 is an overall view of the optical waveguidesheet 10. FIG. 10 is an enlarged view of a second end 10 b of theoptical waveguide sheet 10 opposite to the first end 10 a. FIG. 11A isan enlarged view of part of the optical waveguide sheet 10 enclosed witha one-dot chain line 10A in

FIG. 10. FIG. 11B is a cross-sectional view of the part of the opticalwaveguide sheet 10 taken along a plane including a one-dot chain line11A-11B in FIG. 11A.

Referring to FIGS. 5, 11A and 11B, grooves 16 and slits 17 are providedin the optical waveguide sheet 10. An input/output mirror 14 and analignment mirror 15 are formed in each of the grooves 16. The alignmentmirror 15 is used for alignment of components such as the opticalwaveguide sheet 10, the lens sheet 20, the light-emitting device 41, andthe light-receiving device 42 in the optical waveguide module, andserves as a mark for recognizing the position of the input/output mirror14. In the following, for convenience of description, the grooves 16 andthe slits 17 are described, taking one of the identical opticalwaveguides 11 as illustrated in FIG. 11A as an example.

The groove 16 is formed by forming two inclined surfaces on a secondsurface 10 d of the optical waveguide sheet 10 that is opposite to thefirst surface 10 c. A surface forming the input/output mirror 14 and asurface forming the alignment mirror 15 are substantially at rightangles. The slit 17 is formed by removing part of the optical waveguide11 from the second surface 10 d at a position closer to the second end10 b than is the groove 16. Accordingly, the slit 17 is formed betweenthe second end 10 b and the groove 16.

The groove 16 and the slit 17 are formed by removing part of thecladding 12 and part of the optical waveguide 11 by laser processingusing an excimer laser or the like. The surfaces of the opticalwaveguide 11 formed by the laser processing are flat so as to serve asmirrors. The groove 16 and the slit 17 may also be formed by dicing orthe like.

According to this embodiment, light entering from the first end 10 a ofthe optical waveguide sheet 10 is reflected by the input/output mirror14, and light entering from the second end 10 b of the optical waveguidesheet 10 is reflected by the alignment mirror 15.

Referring to FIG. 5, the input/output mirror 14 causes light emittedfrom the light-emitting device 41 to enter the optical waveguide 11 orcauses light in the optical waveguide 11 to enter the light-receivingdevice 42. The input/output mirror 14 is formed by forming a surfaceinclined substantially at 45° to the second surface 10 d of the opticalwaveguide sheet 10. The lens sheet 20 includes lenses 21, which arepositioned between the optical waveguide sheet 10 and the flexiblesubstrate 30.

According to this embodiment, when the optical waveguide sheet 10 andthe lens sheet 20 are joined, light is caused to enter the opticalwaveguide 11 from the second end 10 b of the optical waveguide sheet 10as indicated by a broken-line arrow A in FIG. 11B. The light enteringthe optical waveguide 11 from the second end 10 b exits from the opticalwaveguide 11 through a first surface 17 a of the slit 17, and reentersthe optical waveguide 11 through a second surface 17 b of the slit 17.Because the core and the cladding 12 are absent in the slit 17, thelight passing through the optical waveguide 11 and exiting from thefirst surface 17 a is diffused in the slit 17, and part of the diffusedlight reenters the optical waveguide 11 through the second surface 17 b.The light reentering the optical waveguide 11 through the second surface17 b is weaker than the light exiting from the first surface 17 a.Therefore, by providing the slit 17, it is possible to reduce the amountof light made incident on the alignment mirror 15.

The light that reenters the optical waveguide 11 through the secondsurface 17 b and propagates through the optical waveguide 11 isreflected by the alignment mirror 15. Because the light made incident onthe alignment mirror 15 is reduced in amount by passing through the slit17, it is possible to reduce scattering light that leaks around theboundary of the alignment mirror 15, so that it is possible to reducecontrast at the time of capturing an image of the alignment mirror 15.

Accordingly, the boundary of the alignment mirror 15 is clarified.

Thus, according to the optical waveguide module of this embodiment, itis possible to perform alignment using light reflected from thealignment mirror 15, and the lens sheet 20 can be accurately alignedwith the optical waveguide sheet 10.

Thus, according to this embodiment, it is possible to align the opticalwaveguide sheet 10, the lens sheet 20, the light-emitting device 41, andthe light-receiving device 42 so that light entering the opticalwaveguide 11 is reflected by the input/output mirror 14 so as to enterthe light-receiving device 42 through the lens 21 or that light emittedfrom the light-emitting device 41 is made incident on the input/outputmirror 14 through the lens 21 so as to be reflected from theinput/output mirror 14 to enter the optical waveguide 11. By joining theoptical waveguide sheet 10, the lens sheet 20, the light-emitting device41, and the light-receiving device 42 that are thus aligned, it ispossible to manufacture an optical waveguide module in which the opticalwaveguide sheet 10, the lens sheet 20, the light-emitting device 41, andthe light-receiving device 42 are positioned as desired.

The above description is given of the case of performing alignment bydetermining the position of the alignment mirror 15 by causing light toenter the optical waveguide 11 through the second end 10 b of theoptical waveguide sheet 10 as indicated by the broken-line arrow A inFIG. 11B. Alternatively, as illustrated in FIG. 12, light may be causedto enter the optical waveguide 11 from the first surface 10 c of theoptical waveguide sheet 10 to which the lens sheet 20 is joined asindicated by a broken-line arrow B. The light entering the opticalwaveguide 11 from the first surface 10 c of the optical waveguide sheet10 as indicated by the broken-line arrow B is reflected by the alignmentmirror 15 so as to propagate through the optical waveguide 11, and isthereafter reflected by the second surface 17 b, which serves as theinterface between the optical waveguide 11 and the slit 17, so as toagain propagate through the optical waveguide 11 to be reflected by thealignment mirror 15 to the side from which the light has entered theoptical waveguide 11. In this case, a light source and a camera forimage recognition may be placed at the same position, so that it ispossible to employ an image recognition camera with a light. Accordingto the image recognition camera with a light, it is possible to adjustthe amount of light of a light source. Accordingly, by adjusting theamount of light entering the optical waveguide 11, it is possible toadjust the amount of light reflected from the alignment mirror 15 to adesired amount.

Second Embodiment

Next, a second embodiment is described. FIG. 13 is an enlarged view ofthe second end 10 b of the optical waveguide sheet 10 according to thisembodiment. FIG. 14A is an enlarged view of part of the opticalwaveguide sheet 10 enclosed with a one-dot chain line 13A in FIG. 13.FIG. 14B is a cross-sectional view of the part of the optical waveguidesheet 10 taken along a plane including a one-dot chain line 14A-14B inFIG. 14A.

According to an optical waveguide module of this embodiment, dummy cores111 that are not used as optical waveguides for propagating opticalsignals are provided in the optical waveguide sheet 10. Referring toFIGS. 14A and 14B, a first groove 116 forming a first alignment mirror115 and a second groove 126 forming a second alignment mirror 125 areprovided in each dummy core 111. Specifically, the first groove 116 isformed on a portion of the first surface 10 c of the optical waveguidesheet 10 where the dummy core 111 is provided, and the second groove 126is formed on a portion of the second surface 10 d of the opticalwaveguide sheet 10 where the dummy core 111 is provided.

The first groove 116 is formed by forming, on the first surface 10 c ofthe optical waveguide sheet 10, a groove whose surface forming the firstalignment mirror 115 is substantially at 45° to the first surface 10 c.The second groove 126 is formed by forming, on the second surface 10 dof the optical waveguide sheet 10, a groove whose surface forming thesecond alignment mirror 116 is substantially at 45° to the secondsurface 10 d. Accordingly, the surface forming the first alignmentmirror 115 and the surface forming the second alignment mirror 125 areformed substantially parallel to each other.

The first groove 116 and the second groove 126 are formed by removingthe cladding 12 and the dummy core 111 by laser processing using anexcimer laser or the like or dicing. The formed inclined surfaces of thedummy core 111 are flat so as to serve as mirrors. Furthermore, becausethe first groove 116 and the second groove 126 are formed by the sameprocessing as the input/output mirrors 14 formed in the opticalwaveguides 11, it is possible to form the first groove 116 and thesecond groove 126 with high accuracy.

According to this embodiment, light enters the optical waveguide sheet10 from the second surface 10 d at a position where the first alignmentmirror 115 is formed as indicated by a broken-line arrow C in FIG. 14B.The entering light is reflected by the first alignment mirror 115 andthe second alignment mirror 125 so as to exit from the first surface 10c of the optical waveguide sheet 10. Components of the optical waveguidemodule are aligned by determining the position of the second alignmentmirror 125 using light exiting from the first surface 10 c of theoptical waveguide sheet 10. Because a common light source such as an LEDmay be used as a light source of the light entering to the opticalwaveguide sheet 10, the amount of light is adjustable. When the amountof light is thus adjustable, it is also possible to reduce lightreflected from the second alignment mirror 125. Therefore, the boundaryof the second alignment mirror 125 is clarified by weakened contrast atthe second alignment mirror 125, so that it is possible to accuratelyalign the optical waveguide sheet 10 and the lens sheet 20.

According to this embodiment, as illustrated in FIG. 15, a planar lightsource 160 may be provided on the second surface 10 d of the opticalwaveguide sheet 10, so that light emitted from the planar light source160 may be reflected by the first alignment mirror 115 so as topropagate through the dummy core 111 to be reflected by the secondalignment mirror 125. By thus employing the planar light source 160, itis possible to easily make light incident on the first alignment mirror115.

Furthermore, according to the optical waveguide module of thisembodiment, the first and second alignment mirrors 115 and 125 mayalternatively be formed in at least some of the optical waveguides 11provided in the optical waveguide sheet 10 as illustrated in FIGS. 16,17A and 17B. FIG. 16 is an enlarged view of the second end 10 b of theoptical waveguide sheet 10. FIG. 17A is an enlarged view of part of theoptical waveguide sheet 10 enclosed with a one-dot chain line 16A inFIG. 16. FIG. 17B is a cross-sectional view of the part of the opticalwaveguide sheet 10 taken along a plane including a one-dot chain line17A-17B in FIG. 17A. Referring to FIG. 17A, the first alignment mirror115 and the second alignment mirror 125 are formed in the opticalwaveguide 11 on the right side for propagating an optical signal.

Referring to FIG. 17, the second groove 126 is formed by two inclinedsurfaces, one of which forms the second alignment mirror 125 and theother of which forms the input/output mirror 14. Furthermore, the secondgroove 126 is formed so that the surface forming the input/output mirror14 and the surface forming the second alignment mirror 125 aresubstantially at right angles. Furthermore, the first groove 116 isformed between the second end 10 b of the optical waveguide sheet 10 andthe second groove 126. Accordingly, in the optical waveguide sheet 10,the first alignment mirror 115 and the second alignment mirror 125 areformed at positions closer to the second end 10 b of the opticalwaveguide sheet 10 than is the input/output mirror 14. In this case,light enters the optical waveguide sheet 10 so as to be reflected fromthe first alignment mirror 115 and the second alignment mirror 125 toexit from the first surface 10 c of the optical waveguide sheet 10 asindicated by a broken-line arrow D in FIG. 17B.

The second embodiment is the same as the first embodiment except for theconfiguration described above.

Third Embodiment

Next, a third embodiment is described. FIG. 18 is an enlarged view ofthe second end 10 b of the optical waveguide sheet 10. FIG. 19A is anenlarged view of part of the optical waveguide sheet 10 enclosed with aone-dot chain line 18A in FIG. 18. FIG. 19B is a cross-sectional view ofthe part of the optical waveguide sheet 10 taken along a plane includinga one-dot chain line 19A-19B in FIG. 19A.

According to an optical waveguide module of this embodiment, dummy cores111 that are not used as optical waveguides are provided in the opticalwaveguide sheet 10 as illustrated in FIGS. 18, 19A and 19B. A firstgroove 216 and a second groove 226 are provided on a portion of thefirst surface 10 c of the optical waveguide sheet 10 where each dummycore 111 is provided, and a third groove 236 and a fourth groove 246 areprovided on the second surface 10 d of part of the optical waveguidesheet 10 where each dummy core 111 is provided as illustrated in FIGS.19A and 19B.

Referring to FIG. 19B, the first groove 216 provided on the firstsurface 10 c and the third groove 236 provided on the second surface 10d are formed at the same position across the dummy core 111. Likewise,the second groove 226 provided on the first surface 10 c and the fourthgroove 246 provided on the second surface 10 d are formed at the sameposition across the dummy core 111. The second groove 226 and the fourthgroove 246 are formed at a position closer to the second end 10 b of theoptical waveguide sheet 10 than are the first groove 216 and the thirdgroove 236. Each of the first groove 216 and the second groove 226 isformed by forming a groove from the first surface 10 c of the opticalwaveguide sheet 10 to a substantial center of the dummy core 111.Furthermore, each of the third groove 236 and the fourth groove 246 isformed by forming a groove from the second surface 10 d of the opticalwaveguide sheet 10 to a substantial center of the dummy core

The first groove 216, the second groove 226, the third groove 236, andthe fourth groove 246 are formed by removing part of the cladding 12 andthe dummy core 111 by laser processing. The method of forming each ofthe grooves 216, 226, 236 and 246 is not limited to laser processing.Furthermore, the surfaces of the dummy core 111 formed by grooveprocessing are flat so as to serve as mirrors. According to thisembodiment, a surface of the first groove 216, a surface of the secondgroove 226, a surface of the third groove 236, and a surface of thefourth groove 246 form alignment mirrors.

According to this embodiment, the first groove 216 and the third groove236 are formed at the same position, and the second groove 226 and thefourth groove 246 are formed at the same position. Therefore, lightentering the optical waveguide sheet 10 from the first surface 10 c canexit from either the first surface 10 c or the second surface 10 d.Likewise, light entering the optical waveguide sheet 10 from the secondsurface 10 d can exit from either the first surface 10 c or the secondsurface 10 d.

Therefore, according to this embodiment, it is possible to cause lightto exit from either the first surface 10 c or the second surface 10 d ofthe optical waveguide sheet 10 in the manufacture of the opticalwaveguide module.

The third embodiment is the same as the first embodiment except for theconfiguration described above.

Fourth Embodiment

Next, a fourth embodiment is described. FIG. 20 is an enlarged view ofthe second end 10 b of the optical waveguide sheet 10. FIG. 21A is anenlarged view of part of the optical waveguide sheet 10 enclosed with aone-dot chain line 20A in FIG. 20. FIG. 21B is a cross-sectional view ofthe part of the optical waveguide sheet 10 taken along a plane includinga one-dot chain line 21A-215 in FIG. 21A.

According to an optical waveguide module of this embodiment, some of theoptical waveguides 11 are provided with the groove 16 in which theinput/output mirror 14 and the alignment mirror 15 are formed and arecognition mark 315 at the center of the alignment mirror 15 asillustrated in FIGS. 20, 21A and 21B.

The groove 16 is formed by forming a groove from the second surface 10 dof the optical waveguide sheet 10 so that a surface forming theinput/output mirror 14 and a surface forming the alignment mirror 15 aresubstantially at right angles. The alignment mirror 15 is formed at aposition closer to the second end 10 b of the optical waveguide sheet 10than is the input/output mirror 14.

The groove 16 is formed by removing the cladding 12 and the opticalwaveguide 11 by, for example, laser processing. Furthermore, therecognition mark 315 is formed by laser processing or the like at thecenter of a surface of the alignment mirror 15. Referring to FIG. 21A,the recognition mark 315 is linearly formed in a width direction of theoptical waveguide 11. According to this embodiment, light entering theoptical waveguide 11 through the first end 10 a is reflected by theinput/output mirror 14, and light entering the optical waveguide 11through the second end 10 b is reflected by the alignment mirror 15.

Light is scattered on part of the alignment mirror 15 where therecognition mark 315 is formed. Accordingly, the part of the alignmentmirror 15 where the recognition mark 315 is formed becomes dark, so thatit is possible to recognize a position of the recognition mark 315 fromthe second surface 10 d of the optical waveguide sheet 10.

Because the recognition mark 315 is formed at the center of thealignment mirror 15, the center of the alignment mirror 15 can bedetermined by focusing on the recognition mark 315, so that it ispossible to increase the accuracy of mounting.

According to this embodiment, when the optical waveguide sheet 10 andthe lens sheet 20 are joined, light enters the optical waveguide 11through the second end 10 b of the optical waveguide sheet 10 asindicated by a broken-line arrow G in FIG. 21B. The light that hasentered the optical waveguide 11 is reflected by the alignment mirror15. Because the recognition mark 315 is formed at the center of thealignment mirror 15, the center of the alignment mirror 15 can berecognized. As a result, it is possible to accurately align the lenssheet 20 with the optical waveguide sheet 10.

The fourth embodiment is the same as the first embodiment except for theconfiguration described above.

Fifth Embodiment

Next, a fifth embodiment is described. FIG. 22 is an enlarged view ofthe second end 10 b of the optical waveguide sheet 10. FIG. 23 is anenlarged view of part of the optical waveguide sheet 10 enclosed with aone-dot chain line 22A in FIG. 22.

According to an optical waveguide module of this embodiment, asillustrated in FIGS. 22 and 23, the optical waveguides 11 are arrangedin the optical waveguide sheet 10 side by side between the two dummycores 111. As illustrated in FIG. 23, the first groove 116 including thefirst alignment mirror 115 and the second groove 126 including thesecond alignment mirror 125 according to the second embodiment areprovided in each dummy core 111.

According to this embodiment, the first alignment mirror 115 and thesecond alignment mirror 125 are formed in each of the dummy cores 111that are provided along each side of the optical waveguides 11. Becausethe alignment mirrors 115 and 125 are formed in the dummy cores 111provided one on each side of the optical waveguides 11, it is possibleto determine the positions of the alignment mirrors 115 distant fromeach other and the positions of the alignment mirrors 125 distant fromeach other, so that the accuracy of alignment can be further increased.

The fifth embodiment is the same as the second embodiment except for theconfiguration described above. Furthermore, the fifth embodiment may beapplied to the optical waveguide module according to the otherembodiments. For example, while the dummy cores 111 are provided one oneach side of the optical waveguides 11 in FIGS. 22 and 23, the firstgroove 116 and the second groove 126 may be formed in each of theoutermost optical waveguides 11 for transmitting optical signals.

Furthermore, the first grooves 116 and the second grooves 126 can beformed in all the optical waveguides 11 including the dummy cores 111.

All examples and conditional language provided herein are intended forpedagogical purposes of aiding the reader in understanding the inventionand the concepts contributed by the inventors to further the art, andare not to be construed as limitations to such specifically recitedexamples and conditions, nor does the organization of such examples inthe specification relate to a showing of the superiority or inferiorityof the invention. Although one or more embodiments of the presentinvention have been described in detail, it should be understood thatthe various changes, substitutions, and alterations could be made heretowithout departing from the spirit and scope of the invention.

What is claimed is:
 1. An optical waveguide module, comprising: anoptical waveguide sheet including a plurality of optical waveguides; alight-emitting device positioned over a surface of the optical waveguidesheet; and a light-receiving device positioned over the surface of theoptical waveguide sheet, wherein at least one of the plurality ofoptical waveguides includes a first mirror configured to reflect lightentering the corresponding optical waveguide from a first end thereof tothe light-receiving device or to reflect light emitted from thelight-emitting device toward the first end of the corresponding opticalwaveguide; a second mirror configured to reflect light entering thecorresponding optical waveguide from a second end thereof opposite tothe first end toward the surface of the optical waveguide sheet; and aslit provided between the second mirror and the second end of thecorresponding optical waveguide, wherein the corresponding opticalwaveguide is discontinuous across the slit.
 2. An optical waveguidemodule, comprising: an optical waveguide sheet including a plurality ofoptical waveguides; a light-emitting device positioned over a firstsurface of the optical waveguide sheet; a light-receiving devicepositioned over the first surface of the optical waveguide sheet; afirst mirror formed in at least one of the plurality of opticalwaveguides and configured to reflect light entering from a secondsurface of the optical waveguide sheet opposite to the first surfacetoward the optical waveguide; and a second mirror formed in the opticalwaveguide and configured to reflect the light reflected from the firstmirror and propagating through the optical waveguide toward the firstsurface of the optical waveguide sheet.
 3. The optical waveguide moduleas claimed in claim 2, wherein the plurality of optical waveguidesinclude a dummy optical waveguide that does not propagate an opticalsignal, and the first mirror and the second mirror are formed in thedummy optical waveguide.
 4. The optical waveguide module as claimed inclaim 2, wherein the plurality of optical waveguides include a firstdummy optical waveguide and a second dummy optical waveguide that do notpropagate an optical signal, the first dummy optical waveguide and thesecond dummy optical waveguide are positioned across the remainingoptical waveguides from each other in a direction of arrangement of theplurality of optical waveguides, and the first mirror and the secondmirror are formed in each of the first dummy optical waveguide and thesecond dummy optical waveguide.
 5. An optical waveguide module,comprising: an optical waveguide sheet including a plurality of opticalwaveguides; a light-emitting device positioned over a surface of theoptical waveguide sheet; a light-receiving device positioned over thesurface of the optical waveguide sheet; a mirror formed in at least oneof the plurality of optical waveguides, the mirror being configured toreflect light propagating through the optical waveguide toward thesurface of the optical waveguide sheet; and a recognition mark providedon the mirror.